It's very fast! Are you caching at all?
Since people probably want to use this with private data, would they usually be sending HTML strings to you, vs URLs?
Why's the "i" in API lower case?
I'm not caching at all since I do not want to store any potential confidential data on my servers. The main reason that it's fast is that there are several instances running Chrome headless behind a load balancer.
The main use case would indeed be to send HTML to the API instead of an URL. I just didn't add this use case to the landing page API tester, but it's definitely supported.
The i in APi is lowercased because I thought it looked cute :)